Fix #3386 - `fixed.to_string`

core/math/fixed/fixed.odin

@@ -102,37 +102,51 @@ round :: proc(x: $T/Fixed($Backing, $Fraction_Width)) -> Backing {
 	return (x.i + (1 << (Fraction_Width - 1))) >> Fraction_Width
 }
 
-
-
 @(require_results)
 append :: proc(dst: []byte, x: $T/Fixed($Backing, $Fraction_Width)) -> string {
+	Integer_Width :: 8*size_of(Backing) - Fraction_Width
+
 	x := x
 	buf: [48]byte
 	i := 0
-	if x.i < 0 {
+
+	if !intrinsics.type_is_unsigned(Backing) && x.i == min(Backing) {
+		// edge case handling for signed numbers
 		buf[i] = '-'
 		i += 1
-		x.i = -x.i
-	}
+		i += copy(buf[i:], _power_of_two_table[Integer_Width])
+	} else {
+		if x.i < 0 {
+			buf[i] = '-'
+			i += 1
+			x.i = -x.i
+		}
 
-	integer := x.i >> Fraction_Width
-	fraction := x.i & (1<<Fraction_Width - 1)
+		when size_of(Backing) < 16 {
+			T :: u64
+			append_uint :: strconv.append_uint
+		} else {
+			T :: u128
+			append_uint :: strconv.append_u128
+		}
 
-	s := strconv.append_uint(buf[i:], u64(integer), 10)
-	i += len(s)
-	if fraction != 0 {
-		buf[i] = '.'
-		i += 1
-		for fraction > 0 {
-			fraction *= 10
-			buf[i] = byte('0' + (fraction>>Fraction_Width))
+		integer := T(x.i) >> Fraction_Width
+		fraction := T(x.i) & (1<<Fraction_Width - 1)
+
+		s := append_uint(buf[i:], integer, 10)
+		i += len(s)
+		if fraction != 0 {
+			buf[i] = '.'
 			i += 1
-			fraction &= 1<<Fraction_Width - 1
+			for fraction > 0 {
+				fraction *= 10
+				buf[i] = byte('0' + (fraction>>Fraction_Width) % 10)
+				i += 1
+				fraction &= 1<<Fraction_Width - 1
+			}
 		}
 	}
 
-
-
 	n := copy(dst, buf[:i])
 	return string(dst[:i])
 }
@@ -146,3 +160,137 @@ to_string :: proc(x: $T/Fixed($Backing, $Fraction_Width), allocator := context.a
 	copy(str, s)
 	return string(str)
 }
+
+
+@(private)
+_power_of_two_table := [129]string{
+	"0.5",
+	"1",
+	"2",
+	"4",
+	"8",
+	"16",
+	"32",
+	"64",
+	"128",
+	"256",
+	"512",
+	"1024",
+	"2048",
+	"4096",
+	"8192",
+	"16384",
+	"32768",
+	"65536",
+	"131072",
+	"262144",
+	"524288",
+	"1048576",
+	"2097152",
+	"4194304",
+	"8388608",
+	"16777216",
+	"33554432",
+	"67108864",
+	"134217728",
+	"268435456",
+	"536870912",
+	"1073741824",
+	"2147483648",
+	"4294967296",
+	"8589934592",
+	"17179869184",
+	"34359738368",
+	"68719476736",
+	"137438953472",
+	"274877906944",
+	"549755813888",
+	"1099511627776",
+	"2199023255552",
+	"4398046511104",
+	"8796093022208",
+	"17592186044416",
+	"35184372088832",
+	"70368744177664",
+	"140737488355328",
+	"281474976710656",
+	"562949953421312",
+	"1125899906842624",
+	"2251799813685248",
+	"4503599627370496",
+	"9007199254740992",
+	"18014398509481984",
+	"36028797018963968",
+	"72057594037927936",
+	"144115188075855872",
+	"288230376151711744",
+	"576460752303423488",
+	"1152921504606846976",
+	"2305843009213693952",
+	"4611686018427387904",
+	"9223372036854775808",
+	"18446744073709551616",
+	"36893488147419103232",
+	"73786976294838206464",
+	"147573952589676412928",
+	"295147905179352825856",
+	"590295810358705651712",
+	"1180591620717411303424",
+	"2361183241434822606848",
+	"4722366482869645213696",
+	"9444732965739290427392",
+	"18889465931478580854784",
+	"37778931862957161709568",
+	"75557863725914323419136",
+	"151115727451828646838272",
+	"302231454903657293676544",
+	"604462909807314587353088",
+	"1208925819614629174706176",
+	"2417851639229258349412352",
+	"4835703278458516698824704",
+	"9671406556917033397649408",
+	"19342813113834066795298816",
+	"38685626227668133590597632",
+	"77371252455336267181195264",
+	"154742504910672534362390528",
+	"309485009821345068724781056",
+	"618970019642690137449562112",
+	"1237940039285380274899124224",
+	"2475880078570760549798248448",
+	"4951760157141521099596496896",
+	"9903520314283042199192993792",
+	"19807040628566084398385987584",
+	"39614081257132168796771975168",
+	"79228162514264337593543950336",
+	"158456325028528675187087900672",
+	"316912650057057350374175801344",
+	"633825300114114700748351602688",
+	"1267650600228229401496703205376",
+	"2535301200456458802993406410752",
+	"5070602400912917605986812821504",
+	"10141204801825835211973625643008",
+	"20282409603651670423947251286016",
+	"40564819207303340847894502572032",
+	"81129638414606681695789005144064",
+	"162259276829213363391578010288128",
+	"324518553658426726783156020576256",
+	"649037107316853453566312041152512",
+	"1298074214633706907132624082305024",
+	"2596148429267413814265248164610048",
+	"5192296858534827628530496329220096",
+	"10384593717069655257060992658440192",
+	"20769187434139310514121985316880384",
+	"41538374868278621028243970633760768",
+	"83076749736557242056487941267521536",
+	"166153499473114484112975882535043072",
+	"332306998946228968225951765070086144",
+	"664613997892457936451903530140172288",
+	"1329227995784915872903807060280344576",
+	"2658455991569831745807614120560689152",
+	"5316911983139663491615228241121378304",
+	"10633823966279326983230456482242756608",
+	"21267647932558653966460912964485513216",
+	"42535295865117307932921825928971026432",
+	"85070591730234615865843651857942052864",
+	"170141183460469231731687303715884105728",
+}